1. Field of the Invention
The present invention relates to a charging circuit. More specifically, the present invention relates to a charging circuit, and method of implementing the same, that can be used in a defibrillator with a more efficient charge time.
2. Description of the Related Art
FIG. 1 illustrates a conventional charging system having a step-up voltage capability using two linked inductive windings, e.g., a transformer, primary winding 10 and secondary winding 12, between a charging voltage source 20 and a utilization device 40. This arrangement was disclosed in FIG. 1 of U.S. Pat. No. 4,070,699, to Einbinder. As set forth in U.S. Pat. No. 4,070,699, to charge capacitor 30, switching circuit 14 is closed and voltage is applied across primary winding 10. Switching circuit 14 is then opened and the energy accumulated in primary winding 10 is transferred to secondary winding 12, charges capacitor 30, which ultimately supplies voltage to utilization device 40. Likewise, upon a closing of switching circuit 14, energy transfers back from secondary winding 12 to primary winding 10. Energy is basically in one winding at a time. U.S. Pat. No. 4,070,699 also notes that it is beneficial to prevent current in the circuit containing secondary winding 12, diode 18, and capacitor 30 from reaching a zero level, which would result in the flux density for primary and secondary windings 10 and 12 going to zero. The benefit of keeping the flux density between primary and secondary windings 10 and 12 sufficiently high is that greater power can be transferred between inductors 10 and 12. To accomplish this, U.S. Pat. No. 4,070,699 recommends closing switching circuit 14 when current in the secondary winding 12 circuit drops to a predetermined level. Usually this level corresponds to the flux density for the primary and secondary windings dropping to two thirds of the saturation level.
Some recent charging systems allow the flux density between primary and secondary windings 10 and 12 to drop to zero by waiting a predetermined time before closing the switching circuit, this predetermined time is meant to correspond to a period of time at which the current flow in secondary winding 12 would typically have extinguished. Thus, though less efficient, recent charging systems typically allow current flow in secondary winding 12 to be extinguished since it is difficult to determine the current flow in secondary winding 12 without permeating noise into circuits connected to secondary winding 12. Utilization device 40 could include delicate sensors for measuring vital health statistics of a patient, for example, when the charging system is for a defibrillator. Thus, recently it has become more important to have secondary winding 12 mostly isolated from primary winding 10, rather than have a more efficient transfer of power between primary and secondary windings 10 and 12. Magnetic field sensing circuit 16, illustrated in FIG. 1, does not allow for such recently necessitated isolation between primary and secondary windings 10 and 12. In addition, although isolation between primary and secondary windings 10 and 12 is important, most recent charging circuits do not have truly isolated primary and secondary windings 10 and 12 since they attempt to sample the voltage in the secondary winding circuitry using a resistor bridge between the circuits connected to primary and secondary windings 10 and 12, which in actuality is not an isolation of primary and secondary windings 10 and 12, though the resistor bridge is designed to minimize cross talk between the circuits connected to primary and secondary windings 10 and 12 as much as possible.
Thus, what is needed is an improved charging system that has a more efficient transfer of power and a truly isolated primary and secondary sides.
To solve the above and other aspects, it is an object of the present invention to provide an improved charging circuit, and method for implementing the same, including a primary switching circuit that controls the transfer of energy between windings in a transformer based upon a reconstruction of a secondary winding current, using a voltage across a primary winding of the transformer, without directly sampling the secondary winding current.
A further object of the present invention is to provide a charging circuit having a transformer having at least primary and secondary windings and a switch to cease an energy transfer between the primary and secondary windings based upon a reconstruction of an unsampled energy level in the secondary winding.
Another object of the present invention is to provide a charging circuit having a transformer having at least primary and secondary windings and a switch to cease an energy transfer between the primary and secondary windings based upon a reconstruction of an unsampled energy level in the secondary winding, wherein the switch ceases the energy transfer when the reconstructed energy level in the secondary winding is a current indicating that a flux density in the transformer has lowered to a predetermined flux density level.
An additional object of the present invention is to provide a charging circuit having a transformer including at least primary and secondary windings and a switch to control a charging of the primary winding until an energy level in the primary winding reaches a predetermined charging level and to control a transfer of energy between the primary and secondary winding until a reconstructed energy level, of an unsampled energy level in the secondary winding, indicates that that a flux density of the transformer has lowered to a predetermined flux density level.
An additional object of the present invention is to provide a charging circuit having a transformer including at least primary and secondary windings and a switch to control a charging of the primary winding until an energy level in the primary winding reaches a predetermined charging level and to control a transfer of energy between the primary and secondary winding until a reconstructed energy level, of an unsampled energy level in the secondary winding, indicates that that a flux density of the transformer has lowered to a predetermined flux density level, wherein the reconstructed energy level is generated by sampling a voltage representative of a voltage across the primary winding and integrating the sampled voltage.
Another object of the present invention is to provide a charging method, including charging a primary winding of a transformer until an energy level of the primary winding reaches a predetermined charge level, and transferring energy between the primary winding and a secondary winding of the transformer until a reconstructed energy level, of an unsampled energy level of the secondary winding, reaches a predetermined energy level.
Another object of the present invention is to provide a charging method, including charging a primary winding of a transformer until an energy level of the primary winding reaches a predetermined charge level, transferring energy between the primary winding and a secondary winding of the transformer until a reconstructed energy level, of an unsampled energy level of the secondary winding, reaches a predetermined energy level, initiating the charging of the primary winding after the transferring of energy between the primary winding and the secondary winding has ceased, and repeating the charging of the primary winding, the transferring of the energy between the primary winding and the secondary winding, and the initiating of the charging of the primary winding until a total charge amount is accumulated in a circuit connected to the secondary winding.
These together with other aspects and advantages which will be subsequently apparent, reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.